Annular tears in the dorsolumbar spine.

As part of a systemic study of the spine between D11 and S1 the distribution and severity of anterior and posterior annular tears has been assessed by charting the tears in sagittal slabs of 117 fresh specimens. No significant sex difference was seen. The number of cases with tears in multiple discs increases with age, but exceptions to this trend occurred in both young and elderly spines. Age adjusted correlation coefficients indicate that anterior and posterior tears at L4 and L5 do not predict tears at other levels. At L3 and above, significant positive correlations occur between multiple disc levels, particularly posteriorly. In patients 50o year old or more the mean anterior tear score rises sharply from L5 to peak at L2 and L1, but, in contrast, the mean posterior tear score falls from L4 to L1 in this age group. The increase in severity of anterior tears corresponds with increased mobility in the L4-L1 disc from 50-70 years. The data are compatible with 2 factors causing tears. One affects L4 and L5 in young adults and is possibly mechanical in nature; the second operates at a later age, promotes widespread disc involvement, and is primarily degenerative in nature. The increased prevalence and severity of anterior tears (and the associated increase in mobility) in the upper lumbar region in the middle aged and elderly may be a pathogenic factor in back pain for this age group.